High vacuum distillation



Dec. 10, A1940. V, VOORHEES 2,224,621

HIGH VACUUM DISTILLATION Filed June 20, 1958 To Vacuunz B ATTORNEYPatented Dec. 10, v1940 HIGH VACUUM DISTILLATION Vanderveer Voorhees,Hammond, Ind., alsignor to Standard Oil Company, Chicago, lll., acorporation of Indiana Application June 20, 1938, Serial N0. 214,682

19 Claims.

This invention relates to a process and apparatus for distilling oils,and particularly for distilling heavy high boiling petroleum oils andlubricating oils. One object of the invention is to distill high boilingsubstances under high vacuum without decomposition. Another object is todistill high boiling substances under so-called mo' lecular distillationconditions without ebullition and without entrainment and contaminationof the distillate bythe undistilled oil. Still another object of theinvention is to provide ameans for Refemngto the drawing, Figure 1', a.sneu It is connected to an exhausting vacuum pump or pumps not shown bymeans of largevacuum connections II and- I2. Alternative orsupplementary connections to the exhausting means may be made on otherparts of the shell, for example to the sides thereof. Within the gastight shell I is located stationary condenser element I3 suitably formedof a perforated cylinder provided with a cooling coil I4 in heatconductive contact therewith. The cooling coil, for example, may beaQPPel' tube spiral soldered to the interior surface of the condensercylinder. The surface I5 of the condenser I3 is provided with openingsI6 to permit free passage of gases and liquids from the exterior to theinterior thereof. Collector bafiies I1 and I8 serve to direct liquidcondensate away from the interior surface of the condenser and into thereceiving funnel I9 whence the liquids ilow by line 20 to suitablereceiver not shown. Connections 2| and 22 serve to supply cold water,oil, brine or other-suitable cooling fluid to the coil` I 4. Thedirection lof ow of the cooling fluid may be either to the top of thecondenser or to the bottom.

Surrounding condenser I3 is evaporator 23 which is 1supported by spiderV24 and bearing 25 providing for free rotation about its axis. Power forrotating cylinder 23 is provided' by motor 26 through the geared pulley2l and belted pulley 28. Obviously, various other means may be employedfor providing rotation. In the arrangement shown a packing gland 29prevents ingress of air through the shell I0 to the evacuated spacewithin, although I may'mount the motor inside casing I0 and 'thusavoidany possibility of air leakage whatever.

Heat is -supplied to thesurface of'evaporator 23 preferably byelectrical induction heater or electrical resistance winding, the latterbeing illustrated in the drawing. A current of electricity supplied bylead wires 30 and 3l passes through the shell III by' insulatedconductors 32 and 33. Brushes 34 and 35 bearing on suitable collectorrings 36 and 3l conduct the electric current to resistance winding I8which is suitably disposed along the outer surface of evaporatingcylinder 22 to provide the heat necessary for distilling oil or otherliquid on the interior surface thereof. Additional electricalconnections may be provided to facilitate regulation of the heatsupplied to evaporator 23. Thus separate coils may be provided atintervals along the surface of the evaporator to separately controlthetemperature in different sections as indicated by suitabletemperature indicating means notshown. Thus the temperature may begraduallyincreased as one progresses from the upper end 20 to the lowerend of the evaporator 23 or,if desired, the temperature may be heldsubstantially constant throughout.

The oil to be distilled is supplied by line 39,

- controlled by valve 4l leading to preheater chamber 4I. The oil may bepreheated in chamber 4I by heating element 42 to a suitable temperaturewell below its decomposition pointffor example 500 to 650 F. in the caseof heavy mineral oils. Any vapors evolved from the oil in the preheater4I are exhausted by line 43 connected to a vacuum pump not shown. It ispreferred to exhaust the preheater 4I to a pressure as low as thatwithin the shell I0. A From .4I the oil flows by line 44 to sight vfeed45 and thence by line 46 to'the upper en'd of evaporator 23. The oil issuitably introduced into the evaporator by allowing it to iiow intochannel member 4l where-it collects by virtue of the action of thecentrifugal force resulting from the rotation of evaporator 23hereinbefore mentioned. From channel 41 the oil flows in a uniformlythin iilm downward over the inner surface of evaporator 23, finallypassing out at the bottom over lip 43. Trough 43 collects the residualoil from which it is conducted by outlet line III.

' Various other means may be employed for supporting the evaporating andcondensing surfaces 23 and I4.l For example, in Figure 2 the hollow 50stationary shaft 80 supports condensing surface 6I by spiders, andevaporating suace I3 is rotated thereabout on bearings 64 and Il.Cooling water for the -condenser is supplied through the hollow shaft 80entering at one end and passing by connection l0 to coil l1 and thenceby connection 63 to the supporting shaft Il and out at the other end.

, Referring again to Figure 1 the inner surface of the revolvingevaporator 2l is preferably pol- U rosion resistant alloy, such asstainless steel.

'I'he exterior surface-I5 of the condenser I3 is likewise preferablypolished to prevent absorption of radiant heat. The surface of theevaporator 23 may be truly cylindrical throughout its length or, ifdesired, it may be slightly conical with the apex in eitherV direction,but preferably toward the top, thus providing more rapid flow of liquiddownward along the surface. In that caseLthe condenser I3 shouldlikewise be conical to correspond therewith. v

'I'he distance separating the condensing surface I5 from the evaporatingsurface 23 is preferably very short, in order to provide a minimumdistance for evaporated oil molecules to travel from the heated surfaceto the cold condensing element 23 of my vacuum distillation'apparatussurface. It is preferred to adjust the surfaces so that the distancesbetween the evaporator and condenser approximate the mean free path ofthe oil molecules under the conditions of temperature and pressureprevailing. However, much larger distances may be employed, for example,up to fifty or even one hundred times the mean free path of themolecules. Thus, distances of 0.05 to 0.4 inch are contemplated.

It is not necessary to rotate the evaporating at veryt high speeds inorder to maintain a uniform lm of oil on the interior surface thereof.

For example, I may operate with speeds of only 200 to 600 revolutionsper minute. At such speeds of rotation the oil is distributed'in auniform film over the inner surface making it possible to adjust thespace between the evaporator and the condenser very closely andaccurately without contamination of the distillate on thecondenseroccurring as a result of physical contact betweenirregularities on the distilling surface. The rotating motion alsoserves to provide agitation of the oil, thus exposing continually new'illm surface to evaporation. ,l

Gases dissolved in the oil and any-vaporous decompositionproduct.thereofAwhich may be liberated at the distunng surface andy s ready l may beemployed, asuitablepressure for most purposes being 0.01 mm. of mercury.One of the important advantages of my vacuum stillation apparatus liesinthe equalization of pressure therein by use of unobstructed gaspassages from evaporatingsurface to vacuum pump, thus providingsubstantially the same pressure at the evaporating surface as atthevacuum pump.

If desired, I may rotate the evaporating element of-my apparatus atsufficient speed to build up by centrifugal action, increased pressurewithin the oil film adjacent the surface of the evaporator 23 thusretarding ebullition of the oil and permitting the use of somewhathigher temperatures without entrainrnent dimculty. By this means thedevelopment of 'a vapor phase within the oil lm in contact with themetallic heating surface is avoided and superheating 'of the body of oilwithin the oil film, above its boiling point at the low pressureprevailing, is made possible. v

Although I have described my invention with respect to certainembodiments thereof lt should be understood that various modincationsmay be employed without departing from the spirit thereof. Thus I- mayemploy in a series two or more distillation units, as described,conducting theoll from one unit to the next to produces series offractions of increasing molecular weight. I may 'also segregate thedistillate from succeeding sections of the condenser in a single unitfor the same purpose. JI'may charge the apparatus with crude oilresidue, for example, a 40% residue from Pennsylvania or Mid-Continentcrude oil. I may also apply my distillation process todistillationof'other materials, such as c oal tara, vegetableand animal oils, fatsand waxes, foi' example, degras, olive oil, chaulmoogra oil, tung oil,etc. I may also apply my distillation method to the recovery ofvitamines from various products, such as fish liver oils, e.g.,.menhaden,-c od,4 halibut liver oils, irradiated fats, etc. Ingeneral,

the method may be applied to the distillation of any liqueilablesubstances whose separation is desired without decomposition. The methodis particularly valuable for the distillation of lubricating oils whereloss of viscosity from decomposition is a serious objection to the useof ordinary.`distillation methds.

I claim: v- 1. The lprocess of distilling liquids under high vacuumwithout ebullition which comprises main- Ataining a cooled,substantially cylindrical, con.

densing surface positioned to Vpermit withdrawal of condensate andsurrounding said condensing surface in close proximity thereto andconcentric therewith, a heated, rotatable, substantially cylindrical,evaporating surface, introducing a stream of said liquid at a point onthe interior of said evaporating surface, rotating said evaporatingsurface at a speed adapted to subject the liquid to a suicientcentrifugal force to uniformly distribute it over the 'surfacethereoLcollecting and withdrawing distillate from said condensing surface anddischarging unevaporated liquid from said evaporating surface at a pointremote from said point of introduction.

2. The process of claim 1 wherein said distillation is conducted undera. pressure of 0.1-to .00001 mm. mercury pressure. a

3. The process of claim 1 wherein the distillation is conducted under alow pressure of the order of .01 mm. mercury, gases evolved from saidliquid undergoing distillation are permitted to pass through' openingsin said cylindrical condensing surface leading to the interior thereofand thence are discharged from the end thereof.

4. The process of claim 1 wherein said liquid is a petroleum lubricatingoil.

v5. The process of claim 1 wherein said liquid is an animal fat.

6. In a molecular distillation process wherein a nquld is disunedwithout bomng by maintaining'a heated surface thereof in close proximity.to a cooled, condensing surface at alow pressure lof the order of .0.01mm. mercury, the improwe- -ment comprising distributing saidliquidon theinterior surfaceof a heated'revolving cylinder, condensing the vapors ona cooled, condensing,

surface positioned to permit withdrawal of condensate and located withinsaid revolving cylinder and in close proximity to the surface thereofand causing said cylinder to revolve at a rate of speed suicient tosubject the said liquid retained therein to centrifugal force sumcientto retard ebullition of said liquid.

7. In a molecular still wherein a crude, liquid material is distributedover a heated, evaporating surface in closeproximity to a cooled,condensing surface, the improvement comprising a gas-tight shell, aconnection leading from said shell to a gas exhausting means, arotatable, heated, cylindrical, evaporating surface within said shell,a' cooled, cylindrical, condensing surface positioned to permitwithdrawal of condensate and located within said evaporating surface andin close proximity thereto, means for rotating said evaporating surface,mean-s for introducing a stream of liquid onto said evaporating surfacewithin the space between it and the said condensing surface, means forwithdrawing unevaporated residue from said evaporating surface and meansfor withdrawing distillate from said condensing surface. f

8. A molecular still as described in claim 'Iv further characterirfieddn.' that the evaporating and condensing surfaces are vertical.

9. In a molecular still wherein a crude, liquid material is distributedover a heated, evaporating sufacein close proximity to a cooled,condensing surface, the improvement comprising a gas-tight shell, aconnection leading from said lshell to a gas exhausting means, arotatable,

heated, evaporating surface within said shell, a cooled, condensingsurface positioned to permit withdrawal of condensate and located inclose proximity to said evaporating surface and nearer to the axis ofrotation of the evaporating surface than is the evaporating surfaceitself, means for 'rotating said evaporating surface, means forintroducing a liquid onto said evaporating surface -within the spacebetween it and said condensing surface, means for dischargingunevaporated residue from said evaporating surface and means forcollecting and withdrawing distillate from said condensing surface. i

10. The apparatus of claim 9 wherein means are provided for heating saidliquid at a low pressure on the order of .01 mm. mercury before i11-troducing it onto said evaporating surface and means for maintaining apressure 'within said shell of the order of .01 mm.

11. The apparatus of claim 9 wherein said evaporating surface is heatedby electrical means.

v12. In a molecular still wherein a crude liquid material is distributedover a heated, evaporating surface in close proximity to a cooled,condensing surface, the improvement comprising a cylindrical, gas-tightshell, a substantially cylindrical, rotatable, heated, evaporatingsurface within said shell, a substantially cylindrical condenserproviding a cooled, condensing surface positioned to permit withdrawalof condensate and located within said evaporating surface, means forintroducing a. liquid onto said evaporating surface be- .01 mm. mercury.

gases from said evaporatinir surface through said condensing surfacethence through the end of said cylindrical condenser and through saidgastight shell to said gas exhausting means.

13. In a molecular distillation process wherein a liquid is distilledfrom an evaporating surface to a condensing surface without ebullition,the improvement which comprises maintaining the evaporating liquid undera centrifugal pressure in a direction away from .the condensing surface.

14. The process of claim 13 wherein said distillation is conductedunder. a pressure of 0.1 to .00001 mm. mercury pressure.

15. The process of claim 13 is a petroleum lubricating oil.

wherein said liquid 16. The process of distilling liquids under high fvacuum without ebullition which comprises inheated, evaporating surfacewhich is in close proximity to a cooled, condensing surface posi-'tioned to permit withdrawal of condensate and located so that acentrifugal force produced by rotation of the evaporating surfaceoperates in a direction away from said condensing surface, maintainingthe space between the said surfaces under a' high vacuum, rotating saidevaporating surface at a speed adapted to subject the liquid to asumcient, centrifugal force to uniformly distribute said liquid over thesurface thereof, and collecting and withdrawing distillate from saidcondensing surface.

17. In a molecular still wherein a crude, liquid material is distributedover a heated, evaporating surface in close proximity to a cooled,condensing surface,'the` improvement comprising a gas-tight shell, aconnection leading from said shell to a gas exhausting means, arotatable, heated, cylindrical, evaporating surface within said shell, acooled, cylindrical, condensing surface positioned to permit withdrawalof condensate and located within said evaporating surface and in closeproximity thereto, means for rotating said evaporating surface, meansfor introducing a stream of liquid onto said evaporating surface withinthe space between it and the said condensing surface, and means forwithdrawing distillate from said condensing surface.

18. In a molecular still wherein a crude liquid material is distributedover a heated, evaporating surface in close proximity to a cooled,condensing surface, the improvement comprising a gas-tight shell, aconnection leading from said shell to a gas exhausting means, arotatable, heated, evaporating surface within said shell, a cooledcondensing surface positioned to permit Withdrawal vspace between it andsaid condensing surface,

and means for collecting and withdrawing distillate from said condensingsurface.

19. ,The apparatus of claim 18 wherein means are provided for heatingsaid liquid at a low pressure on the order of .01 mm. mercury beforeintroducing it onto said evaporating surface and wherein means are alsoprovided for maintaining a pressure withinl said shell of the order ofVANDERVEER VOORHEES.

